He glided silently underwater past the Statue of Liberty and Coney Island and headed north to Rhode Island, where cold waters could threaten his life.

Chessie, who has gone where no manatee ever went before, is one daring sea cow and has won the admiration of scientists who have been tracking his every twist and turn. Weighing in at 1,250 pounds and as long as a row boat, Chessie also has animal protection services worried that he may have to be airlifted home to Florida unless he starts back-tracking.Manatees are an endangered species and normally live in Florida, rarely venturing north of Georgia, but Chessie has travelled up the intercoastal waterway - a series of rivers, canals and bays along the Atlantic coast.

"Chessie is just a traveling man," said Linda Taylor of the Chesapeake Bay field office of the U.S. Fish and Wildlife Service, where Chessie was first spotted last year. Wildlife officials grew alarmed when Chessie, oblivious to an autumn chill that threatened his life, did not swim home, and they airlifted him back south in a Coast Guard airplane.

But this weekend, back again, he swam as far north as Point Judith, Rhode Isand, at the western edge of Narragansett Bay and then doubled back 35 miles, said Jim Reid of the National Biological Service. Chessie has backtracked before so the next few days will tell if he is returning home or just resting, Reid said.

Scientists hope the cold waters will persuade him to go home on his own this time, but they are ready for another airlift if needed. Chessie was in waters with temperatures below 70 recently, and Reid said manatees cannot survive for extended times in temperatures below 65.

Chessie's entire journey this year is being tracked by satellite by means of a tag tied to his tail last year. The transmitter, designed to fall off if it gets entangled, attracted the attention of two boys in Connecticut last week. Fearing the device would snare the walrus-like creature, they helped lead him out of the docking area.

"He's had a good trip," said Taylor, noting that the wanderer has visited Ocean City, Md., Atlantic City, N.J., and such famed New York tourist attractions as the Statue of Liberty, Ellis Island and Coney Island.